Automatic needle insertion mechanism

ABSTRACT

An automatic needle insertion device for a pen shaped syringe comprising a cartridge holder ( 2 ) wherein a cartridge with a drug can be accommodated, and a dose setting and injection part ( 1 ) by which a wanted dose may be set an subsequently pressed out from the cartridge by pressing a button ( 12 ) projecting from the dose setting and injection part ( 1 ). The device comprises a mainly tubular housing ( 31 ) in which a tubular pen holder ( 22 ) in which a pen can be mounted can be axially displaced in a proximal direction to cock a spring ( 30 ) which can thereafter be released to drive the pen holder ( 22 ) with the pen a set distance in a distal direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.08/887,871 filed Jul. 3, 1997 now U.S. Pat. No. 5,980,491, which claimspriority under 35 U.S.C. 119 of Danish application 0751/96 filed Jul. 5,1996, the contents of which are fully incorporated herein by reference.

The invention relates to automatic needle insertion mechanisms for penshaped syringes comprising a cartridge holder wherein a cartridge with adrug can be accommodated, and a dose setting and injection part by whicha wanted dose may be set an subsequently pressed out from the cartridgeby pressing a button projecting from the dose setting and injectionpart. As it will be understood the dose setting and injection part formsthe more mechanically complicated part of the syringe whereas thecartridge holder is a rather simple tubular part. The designation “penshaped” shall be taken broadly recognising that a pen need not be oblongand have a circular cross section. Syringes designed to apportion anumber of set doses from an ampoule and commonly carried by the user areoften called pens even when they do not have a shape making them looklike a fountain pen as had the first syringes of that kind.

Pen syringes are mainly used by patients to perform self injections. Bysuch handling by non professionals it is important that the handling issimple so that complications are avoided. A phase of the injection uponwhich most people look at with disinclination is the needle insertionphase. This disinclination may incur that the needle insertion is notperformed as purposefully quickly as it is appropriate to obtain aprecise, uncomplicated and painless insertion.

Consequently different apparatus for automatic needle insertion has beenproposed. U.S. Pat. No. 4,787,891 describes an injection apparatus forcommon single dose syringes. In this apparatus the syringe is mounted ina holder which against the force of a spring may be drawn into a barreland locked in its retracted position. When the barrel is placed wherethe. needle insertion is wanted and the lock is released, the holderwith the syringe is forced forwards by the spring and a needle mountedon the syringe will project from the end of the barrel and pierce theskin where the barrel is placed.

From WO 88/08725 a pen shaped syringe is known wherein an automaticneedle insert mechanism is integrated. The spring which provides theforce necessary to insert the needle is further used to inject a setdose of medicine from the ampoule in the pen syringe. However, users mayprefer to perform the injection themselves as this offers a possibilityof adjusting the injection speed in accordance with the receivingability of the tissue so that tensions and infiltrations are avoided.

Also pen shaped syringes with integrated needle insertion mechanisms butwithout automatic injection are known. Consequently, it is possible tobuy pen syringes with built in needle insertion mechanisms.

If one has a pen syringe without such a mechanism, it will be attractiveto have a separate needle insertion mechanism in which a pen shapedsyringe may be mounted. This will give the user a freedom to the extenthe may want to sometimes use a pen with and sometimes a pen without anautomatic needle insertion mechanism.

The object of the invention is to provide such an automatic needleinsertion mechanism for a syringes by which more individually set dosesmay be apportioned from a cylinder ampoule which can be changed whenempty.

This is obtained by a pen shaped syringe of the kind described in theopening of this application, which syringe is according to the inventioncharacterised in that the device comprises a mainly tubular housing inwhich a tubular pen holder in which a pen can be mounted can be axiallydisplaced in a proximal direction to cock a spring which can thereafterbe released to drive the pen holder with the pen a set distance in adistal direction. It shall be noticed that the designation “tubular”does not necessarily involve a tube having a circular cross section, thetube may have any appropriate cross section, e. g. a rectangular crosssection.

In an appropriate embodiment of the invention the pen holder is shapedas a cartridge holder and only the dose setting and injection part ofthe pen syringe is mounted in the pen holder.

The cartridge holder forms a simple and inexpensive part of the pensyringe which part is designed to be in a simple way dismounted from thesyringe when a new cartridge is going to be mounted. A cartridge holderwith an automatic needle insertion mechanism can be seen as a spare partwhich can replace the common cartridge holder. If later a syringewithout auto insertion device is wanted, the cartridge holder may againbe replaced by the original simple one.

In a further appropriate embodiment of the mechanism according to theinvention the cartridge holder shaped pen holder may at a proximal endhave an inner thread in which an outer thread of the dose setting andinjection part of a pen may be received.

According to the invention the pen holder may be provided withinspection windows to allow the same inspections as do a commoncartridge holder. This way confusion of a user who is familiar with thepen with the original cartridge holder is avoided. It is an advantagethat the means for operating the needle insertion device are firmlyconnected with the pen holder so that no superfluous operating means areleft on the pen syringe when the pen holder with the automatic needleinsertion device is replaced by the original cartridge holder.

According to an embodiment of the invention the distal end of thetubular housing of the automatic needle insertion device may beobliquely cut to allow abutment against the skin at an angle so that theneedle may be inserted at an angle of about 45°.

In the following the needle insertion mechanism according to theinvention will be described with reference to the drawing, wherein

FIG. 1 shows a common known pen shaped syringe for the delivery setdoses of medicine from a cartridge,

FIG. 2 shows a sectional view of an automatic needle insertion devicewith a cartridge holder shaped pen holder.

FIG. 3 shows a pen shaped syringe mounted with the pen holder shown inFIG. 2, with the needle insertion mechanism uncocked, and

FIG. 4 the device in FIG. 3 with the needle insertion mechanism cocked.

FIG. 1 shows schematically a pen shaped syringe for injection of setdoses of medicine from a cartridge. The syringe consists of a dosesetting part 1 comprising a housing containing a dose setting mechanismin which an intended dose may be set by turning a dose setting knob 12.During the setting of the dose the knob 12 is elevated from the housing11 a distance proportional with the size of the dose set. When the knob12 is pressed back to abutment with the housing, a piston rod 13extending from the housing will be driven further out from the end ofthe housing opposite the knob 12 another distance proportional with theset dose. An external thread 14 at the end of the housing from which thepiston rod projects serves the connection of said housing with acartridge holder 2.

The cartridge holder 2 has at an end 21 an internal thread for thereceipt of the external thread 14 of the dose setting part 1. Thecartridge holder 2 has a tubular body 22 wherein a cartridge of the kindwhich is at an output end closed by a rubber membrane and at the otherend closed by a piston may be accommodated with its piston facing theend 21 of the cartridge holder 2. Cut-outs 23 in the wall of the bodyenables inspection of the not shown cartridge mounted in the holder. Theremaining wall of the body is provided with marks 25 indicating how muchmedicine is left in the cartridge when the piston reach the respectivemarks. A further inspection window 24 near the end of the cartridgemakes it possible to inspect the output end of the cartridge to seewhether the cartridge is emptied to an extent that calls for a change ofsaid cartridge.

A cap 3 can cover the cartridge holder and a possible injection needlemounted at the output end of the cartridge so that the pen may be keptfree from dust and the needle is protected.

FIG. 2 shows a sectional view of a cartridge holder into which a needleinsertion mechanism is integrated. Details corresponding to details inthe cartridge holder 2 shown in FIG. 1 is given the same referencenumbers. This goes for the body 22 which however is supplied with anelongation 26 and a collar 27, the marks 25, the inspection window 24and the end 21 in which further an internal thread 28 is seen.

The cartridge holder body is enclosed by two shells which are joinedtogether along their edges to form a housing 31 in which the cartridgeholder body is mounted axially displaceable. Between an inwardprojection 29 in the housing and the collar 27 surrounding the cartridgeholder body a helical spring 30 is mounted surrounding the end of thecartridge holder which carries the internal thread 22 for reception of adose setting part 1. When the cartridge holder body 22 with itselongation is drawn upwards in the housing 31 in FIG. 2, the helicalspring is compressed and when the body is drawn so far that a springring 32 can engage an opening 33 near the upper end of the housing, thecartridge holder body will be held in a cocked position from which itmay be released by pressing a trigger button 34 at the upper end of thehousing 31.

One of the shells forming the housing has at its lower end in FIG. 2 arest piece 35 which may be placed resting against the skin where aninjection is going to be made whereas the lower end of the other shellis without such a rest so that an opening between the skin and the endof the housing is formed for inspection of the needle in its positionready for insertion perpendicularly to the skin. Alternatively the factthat the resting piece lacks on one of the shells allows that thesyringe is held with the rest pjece of one shell and the edge of theshell which has no rest pjece in abutment with the skin so that theneedle pierces the skin at an angle of about 45°. The lower end of thehousing is closed by a protective cap 36 when the device is not in use.

FIG. 3 shows a dose setting part 1 of a pen shaped syringe mounted witha cartridge holder wherein a needle insertion mechanism is integrated.The dose setting part 1 has its external thread 14 screwed into theinternal thread 28 of the cartridge holder. The dose setting part whichproject over the end of the cartridge holder housing forms a good gripby which the cartridge holder body 22 may be drawn upwards in thehousing in FIG. 3 to compress the spring 30 between the collar 27 of thecartridge holder body and the inward projection 29 of the housing 31. Inthe uncocked condition of the device the needle will project beyond therest piece 35 whereas the needle in the cocked condition of the deviceas shown in FIG. 4 will be retracted a short distance behind the outerend of the rest piece.

What is claimed is:
 1. An automatic needle insertion device for use witha pen-shaped syringe of the type including a cartridge holder forholding a cartridge containing a drug to be administered, and adose-setting and injection part by which a desired dose can be set andsubsequently injected, said device comprising: a mainly tubular housinghaving proximal and distal ends, and including a rest portion whichprojects from said distal end in a distal direction and which can beplaced against the skin; a mainly tubular cocking element for releasablyengaging at least one of the parts of a syringe of the type described inthe preamble such that a proximal end of the dose-setting and injectionpart projects from a proximal end of said cocking element, wherein saidcocking element is mounted in said tubular housing so as to be axiallydisplaceable therein; a spring having opposite ends engaging,respectively, said tubular housing and said cocking element such thatmoving the cocking element in a proximal direction relative to saidhousing cocks said spring; wherein said cocking element is axiallymoveable between an injection position and a cocked position such that,when a syringe having a needle provided thereon is mounted in saidneedle insertion device, and said cocking member is in said injectionposition, such needle will project in a distal direction beyond saidrest portion by a predetermined distance, and wherein, when said cockingmember is moved in a proximal direction to said cocked position, such aneedle will be retracted to lie a distance in a proximal direction fromsaid rest portion; whereby an injection can be administered by mountinga pen shaped syringe having a needle in said needle insertion device,setting a dose, moving said cocking element to said cocked position,thereby cocking said spring, placing said rest portion against the skin,releasing said cocking element to cause the syringe and needle to movefrom the cocked position to the injection position, thereby causing theneedle to penetrate the skin, and injecting the set dose.
 2. A deviceaccording to claim 1, wherein said cocking element has a window to allowinspection of the cartridge in the syringe.
 3. A device according toclaim 1, wherein said rest portion is provided on only a part of saiddistal end so as to allow a needle mounted on a syringe to pierce theskin at an angle.
 4. An automatic needle insertion device for use with apen-shaped syringe of the type including a cartridge holder for holdinga cartridge containing a drug to be administered, and a dose-setting andinjection part by which a desired dose can be set and subsequentlyinjected, said device comprising: a mainly tubular housing havingproximal and distal ends, and including a rest portion which projectsfrom said distal end in a distal direction and which can be placedagainst the skin; a mainly tubular syringe holder for releasablyengaging a syringe of the type described in the preamble such that aproximal end of the dose-setting and injection part of such syringeprojects from a proximal end of said syringe holder, wherein saidsyringe holder is mounted in said tubular housing so as to be axiallydisplaceable therein; a spring having opposite ends engaging,respectively, said tubular housing and said syringe holder such thatmoving the syringe holder in a proximal direction relative to saidhousing cocks said spring; wherein said syringe holder is axiallymoveable between an injection position and a cocked position such that,when a syringe with a needle is mounted in said syringe holder, and saidsyringe holder is in said injection position, such needle will projectin a distal direction beyond said rest portion by a predetermineddistance, and when said syringe holder is moved in a proximal directionto said cocked position, such a needle will be retracted to lie adistance in a proximal direction from said rest portion; whereby aninjection can be administered by mounting a pen shaped syringe having aneedle in said needle insertion device, setting a dose, moving saidsyringe holder to said cocked position, thereby cocking said spring,placing said rest portion against the skin, releasing said cartridgeholder to cause the syringe and needle to move from the cocked positionto the injection position, thereby causing the needle to penetrate theskin, and injecting the set dose.
 5. A device according to claim 4,wherein said syringe holder has a window to allow inspection of thecartridge in the syringe.
 6. A device according to claim 4, wherein saidrest portion is provided on only a part of said distal end so as toallow a needle mounted on a syringe to pierce the skin at an angle.